Collagen is one of the most abundant forms of animal tissues. Collagen products find numerous medical and bioengineering uses.
Collagen products are used in medicine and dentistry for many purposes, including wound dressings and as matrices for tissue growth. This is because it is the chief structural protein of the body.
Advantages of collagen as a biomaterial
The advantages of using collagen include:
- it is available in abundance and easily puriﬁed from living organisms. More than 30% of vertebrate tissues have collagen.
- orientation of fibers
- semipermeability of membranes
- positive effect on wound healing rates
- non-antigenic - since the fibers are abundant in nature they do not cause a reaction of the immune system.
- non-toxic and biocompatible
- biodegradable and bioreabsorbable - biodegradability can be regulated by cross-linking
- biological plastic due to high tensile strength and minimal expressibility
- synergic with other used bioactive components and compatible with synthetic polymers
- formulated in a number of different forms
- promotes blood coagulation
- easily modiﬁable to produce materials as desired by utilizing its functional groups
Disadvantages of collagen as a biomaterial
The disadvantages of using collagen include:
- high cost of pure type I collagen
- isolated collagen is variable in crosslink density, ﬁber size, trace impurities, etc.
- hydrophilic i.e. absorbs water leading to swelling and release.
- variability in enzymatic degradation rate when compared to hydrolytic degradation
- complex handling properties
- carries a risk of transmitting illnesses such as bovine spongeform encephalopathy (BSF) and mineralization
Industrial uses of collagen
For industrial purposes collagen is denatured by heating. This causes the three tropocollagen strands to separate partially or completely into globular domains, containing a different secondary structure to the normal collagen polyproline II (PPII), e.g. random coils. This is called formation of gelatin.
Gelatin is used in many foods, including flavored gelatin desserts. Besides food, gelatin has been used in pharmaceutical, cosmetic, and photography industries.
Gelatin is a poor source of nutrition and protein since they do not contain all the essential amino acids in the proportions that the human body requires. However, some manufacturers of collagen-based dietary supplements claim that their products can improve skin and fingernail quality as well as joint health. There is no evidence to support these claims.
Collagen was originally used to produce glue. The word collagen is derived from the Greek for glue, ''kolla''. Earlier the skin and sinews of horses and other animals were boiled to obtain glue. Collagen adhesive was used by Egyptians about 4,000 years ago, and Native Americans used it in bows about 1,500 years ago.
The earliest glue isolated is dated around 8,000 years old and is made of collagen. This was used as a protective lining on rope baskets and embroidered fabrics, and to hold utensils together.
Animal glues from collagen are thermoplastic, meaning they dry up and harden and soften on reheating. These are still used in making musical instruments such as fine violins and guitars. Animal sinews and skins, including leather, have been used to make useful articles since ages.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)